From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=FROM_EXCESS_BASE64, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E99B6C3A5A1 for ; Wed, 28 Aug 2019 15:21:47 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id BF29222CED for ; Wed, 28 Aug 2019 15:21:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BF29222CED Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:37642 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i2zla-0001DT-QW for qemu-devel@archiver.kernel.org; Wed, 28 Aug 2019 11:21:46 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41622) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i2zkQ-0000Kn-OP for qemu-devel@nongnu.org; Wed, 28 Aug 2019 11:20:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i2zkP-00081y-0h for qemu-devel@nongnu.org; Wed, 28 Aug 2019 11:20:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34260) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i2zkO-00080z-RR for qemu-devel@nongnu.org; Wed, 28 Aug 2019 11:20:32 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 233E418B3D87; Wed, 28 Aug 2019 15:20:32 +0000 (UTC) Received: from redhat.com (unknown [10.42.17.64]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 689C560C5D; Wed, 28 Aug 2019 15:20:30 +0000 (UTC) Date: Wed, 28 Aug 2019 16:20:28 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Alex =?utf-8?Q?Benn=C3=A9e?= Message-ID: <20190828152028.GM2991@redhat.com> References: <20190823163931.7442-1-berrange@redhat.com> <20190823163931.7442-4-berrange@redhat.com> <878srd5nlz.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <878srd5nlz.fsf@linaro.org> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.63]); Wed, 28 Aug 2019 15:20:32 +0000 (UTC) Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH 3/4] docs: document use of automatic cleanup functions in glib X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Aug 28, 2019 at 04:14:00PM +0100, Alex Benn=C3=A9e wrote: > > +The cleanup functions are not restricted to simply free'ing memory. = The > > +GMutexLocker class is a variant of GMutex that has automatic locking= and > > +unlocking at start and end of the enclosing scope > > + > > +In the following example, the `lock` in `MyObj` will be held for the > > +precise duration of the `somefunc` function > > + > > + typedef struct { > > + GMutex lock; > > + } MyObj; > > + > > + char *somefunc(MyObj *obj) { > > + g_autofree GMutexLocker *locker =3D g_mutex_locker_new(&obj-= >lock) > > + g_autofree char *foo =3D g_strdup_printf("foo%", "wibble"); > > + g_autoptr (GList) bar =3D ..... > > + > > + if (eek) { > > + return NULL; > > + } > > + > > + return g_steal_pointer(&foo); > > + } >=20 > I would personally prefer we get some RFC patches for auto-unlocking un= der our > belt before we codify it's usage in our developer docs. Locking is a > fickle beast at the best of times and I'd like to see where it benefits > us before there is a rush to covert to the new style. >=20 > For one thing the only uses I see of g_mutex_lock is in our tests, the > main code base uses qemu_mutex_lock. How would we go about registering > the clean-up functions for those in the code base? Ideally we could just relpace qemu_mutex with g_mutex, but if that's not possible we would have to create a clone of GMutexLocker as QemuMutexLocker doing exactly the same thing. It is a shame to reinvent the wheel with our threading code though. /me tries to remember what it was that we can do with QEMU's threads that we can't do with GLib's threads. Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberran= ge :| |: https://libvirt.org -o- https://fstop138.berrange.c= om :| |: https://entangle-photo.org -o- https://www.instagram.com/dberran= ge :|